1. Field of the Invention
The present invention relates to shifting actuators for selectively preloading a shifting mechanism to be shifted into a preselected one of at least two selectable operating positions. More particularly, the present invention relates to a shifting actuator for preloading a shifting mechanism to be shifted into a preselected one of at least two selectable operating positions which preferably utilizes a unidirectional rotational motor, preferably an electric motor, to drive a rotatable member, such as a cam, scotch yoke flywheel, or the like, which rotatable member is effective to axially compress a resilient biasing device, preferably a single compression spring, to preload, i.e. resiliently bias, the shifting mechanism toward the selected operating position.
2. Description of the Prior Art
Shift actuators, such as two-position shift actuators, for selectively shifting, or positioning, a shifting mechanism, such as a shift fork or the like, are well known in the prior art. Such mechanisms are typically utilized to engage one of two engagable gears, to engage or disengage a single gear, to engage or disengage a clutch, to engage or disengage a lockup device, such as a differential lockup, or the like. Examples of such devices may be seen by reference to U.S. Pat. Nos. 2,858,714; 3,195,371; 3,368,638 and 4,207,780, all of which are hereby incorporated by reference.
Two-position shift actuators allowing a shift to preselected by preloading of an element, usually a resilient element such as a spring, to bias the shifting mechanism, usually a shift fork, towards a preselected position are also well known in the prior art. Examples of such devices may be seen by reference to U.S. Pat. Nos. 2,754,692; 2,821,089 and 3,358,517, all of which are hereby incorporated by reference.
While the prior art two-position shift actuators allowing a shift to preselected were generally satisfactory, such devices are not totally satisfactory as the devices usually required a bidirectional linear or rotational motor, required or plurality of springs, utilized relatively expensive ball screw devices, utilized torsional springs and/or were undesirably complicated and/or expensive to produce.